1. Field
The disclosed subject matter relates to a vehicle mount and method. More particularly, the disclosed subject matter relates to an engine mount that includes a stopper having a bladder mechanism or fluid cushion system, and method of operation thereof.
2. Brief Description of the Related Art
Engine mounts are typically used to connect a vehicle's frame to the vehicle's power plant. A damper mechanism or brake mechanism can be incorporated into the engine mount to reduce the amount of vibration, motion, and energy transmitted between the vehicle's power plant and the vehicle's body frame. Thus, a driver or operator experiences less noise vibration and harshness when operating the vehicle.
Conventional engine mounts are commonly used as engine, gearing or transmission suspensions in motor vehicles. The action of these mount systems is substantially axial, and in the direction of a longitudinal axis of the engine mount. One end of the mount system can be directly attached to the motor housing/gearing housing/transmission housing/etc., and an opposite end of the mount system can be directly attached to the vehicle body or frame/sub-frame. Many variables, including the weight of the power plant, the amplitude and frequency of vibration produced by the power plant, the type of vehicle, and other variables help to determine the amount of damping that is desirable for the engine mount.
One specific type of engine mount is a hydraulic engine mount. Typically, hydraulic engine mounts include a metal post that is attached to an elastomeric bladder which is then attached to the vehicle frame by another metal structure, such as a cup structure or another metal post, at an opposite end of the bladder. An incompressible fluid is located in the elastomeric bladder to provide the damping desired for a particular application. More advanced hydraulic engine mounts include a bladder or bladders that is/are partitioned into separate chambers. A first working chamber can be defined for damping normal high frequency engine vibrations, road vibration, etc., while a second compensating chamber can be provided for damping lower frequency high amplitude vibration, such as engine start up vibration or road abnormalities impacting on the vehicle suspension. The working chamber and the compensating chamber can be divided by a valve system that control damping openings. During operation, liquid constituents are displaced back and forth through the damping openings, between the working chamber and the compensating chamber, in order to provide the different damping effects.
In the radial direction of the hydraulic engine mount, supporting action has typically been attained by providing hard, rubber spring segments, while damping isolation has been provided by relatively softer, rubber spring segments.
Another even more common engine mount is the standard elastic damper that has a connection post extending from either end of a damping material for connection between the vehicle power system and the vehicle frame or body. The shape and type of material selected for the damping material provide the desired damping effect.
Other common vehicle mounts include suspension compliance bushings, sub-frame mounts, and differential mounts.
In the conventional engine mounts, little thought has been put into the ultimate motion limits for the components of the engine mount. Usually, a rigid structure is placed a predetermined distance from one of the moving structures of the engine mount such that if the movement of these moving structures exceeds a predetermined amount, a portion of the moving structures contacts the rigid structure to limit relative movement beyond that predetermined amount. For example, conventional art such as U.S. Pat. No. 6,557,839 discloses a fluid filled vibration damping device that includes a stop member 88 connected to a stud 22 such that if the stud 22 moves beyond a certain range of motion with respect to a bracket 90 (and vehicle frame), the stop member will contact an abutting portion 100 to limit the movement. A rubber buffer 94 is located on the stop member 88.
The above described conventional engine mounts operate well when their constituent parts do not move relative to each beyond a certain range of movement. However, in the event that a stop member must be used to limit the movement during operation, conventional engine mounts sometimes create unwanted noise, harshness or vibration that is transmitted to the vehicle and to the operator of the vehicle. In addition, use of the stop member sometimes results in damage to vehicle components due to the almost instant deceleration of sophisticated engine or operating components of the vehicle.